Project summary Type-2 inflammation, characterized in part by the production of cytokines IL-5 and IL-13, is a hallmark feature of asthma. Recently, the innate and adaptive immune systems have been shown to play critical roles in coordinating the development and propagation of type-2 inflammation in the airways. Previous discoveries by our group and others have revealed that secreted PLA2 (sPLA2) activity is increased in the airways of asthmatics, with much of the observed sPLA2 activity attributed to one member in particular, sPLA2 group X (sPLA2-X), which is primarily expressed by epithelial cells and macrophages. Enzymatic activity of sPLA2-X contributes to the pool of eicosanoids in the airways, but the function of sPLA2s beyond their enzymatic activity is not well understood. Because of the established involvement of sPLA2-X in settings of human asthma, we seek to better define the function of sPLA2-X during allergic inflammation of the airways using in vivo models of experimental asthma. Our preliminary data suggest that 1) genetic ablation of sPLA2-X protects against the development of a type-2 immune response and 2) sPLA2-X given as an adjuvant promotes both innate and adaptive components of type-2 inflammation. In this application, we seek to uncover the mechanism by which sPLA2-X initiates a type-2 immune response in the airways. Our primary hypothesis is that sPLA2-X acts as an adjuvant to enhance type 2 immune responses through the release of epithelial derived cytokines including IL-33 and polarization of ILC2s. We further postulate that TGM2 serves to augment the function of sPLA2-X during the development of allergic inflammation. In Aim 1, we focus on the importance of IL-33 in driving type-2 inflammation and ILC2 polarization using a sPLA2-X/OVA model of experimental asthma. Using murine and human airway epithelial cells, we examine the specific contribution of epithelial sPLA2-X function in the release and expression of epithelial-derived cytokines that promote type-2 inflammation. In Aim 2 we examine the involvement of TGM2 in the development of type-2 inflammation and whether TGM2 acts by regulating sPLA2-X activity. Completion of these studies will provide a more thorough understanding of sPLA2-X function in allergic lung disease and further validation of sPLA2-X as a novel therapeutic target in settings of asthma.